1. Field of the Invention
This invention relates to an image capture system for capturing image signals representative of a plurality of divided images of an object photographed by a camera.
2. Description of the Prior Art
An inspection step for circuit substrates is conventionally provided with an inspection system including a camera for photographing wire-bonded parts or portions etc. of a substrate surface, for example. In this inspection system, an image of a minute wire-bonded part is difficult to be recognized when the overall circuit substrate is photographed so as to come into the range of the camera. Accordingly, parts of the circuit substrate to be inspected are photographed as respective enlarged images. The circuit substrate usually includes a plurality of parts to be inspected. The camera or the circuit substrate is moved horizontally so that different parts to be inspected are photographed.
In the above-described inspection system, however, it is difficult to capture images of a plurality of different parts to be inspected at high speeds since moving the camera or the circuit substrate takes much time. Consequently, the above-described inspection system cannot meet the requirement of high speed processing.
To solve the above-described drawback, the prior art has provided a system in which a plurality of cameras are set for each of the parts to be inspected so that images of different parts photographed by the respective cameras are captured. In this system, however, a plurality of cameras cannot be juxtaposed when the parts to be inspected are located near to one another. Accordingly, this system cannot be applied to an inspection system for small components such as the circuit substrates.
Japanese Unexamined Patent Publication No. 8-233554 (1996) discloses a system including two galvanometer mirrors disposed above the object to be inspected. A part of the object is reflected on the galvanometer mirrors in turn, and angles of the galvanometer mirrors relative to the object is switched at a predetermined frequency so that the part of the object to be reflected on the galvanometer mirrors is changed. Two lenses are disposed in front and in the rear of the galvanometer mirrors respectively. Parts of the object reflected on the galvanometer mirrors in turn are sequentially photographed by the camera in synchronization with the changes in the angles of the galvanometer mirrors. Consequently, images of the entire object with a large area can be captured at a high speed.
In the disclosed system, one of the galvanometer mirrors has a wide changing range of its angle (swing angle) for the purpose of photographing an object with a large area. Accordingly, a distance between the part to be photographed and the galvanometer mirror is varied to a large extent with the change in the angle of the galvanometer mirror. This results in variations in the length of an optical path between the part to be photographed and the camera to a large extent. The variations in the length of the optical path result in an unfocused image photographed by the camera. In the disclosed system, the two lenses are disposed in front and in the rear of the galvanometer mirrors respectively to compensate a focal length. However, provision of these lenses complicates the arrangement of the optical system and increases the cost of the system.